Duct-forming devices



June `2O, 1967 S. M. ZANDMER DUCT-FORMING DEVICES Filed Nov. 12, 1964 A Km v WW@ 7 vm?) i' @ww invent mf f FIG.l 3

United States Patent 3,326,291 DUCT-FRMING DEVICES Solis Myron Zandmer, Banff, Alberta, Canada Filed Nov. 12, 1964, Ser. No. 410,352 6 Claims. (Cl. 16d- 100) This invention relates to a duct-forming device for the lbore hole casing or liner of oil wells.

By duct-forming device is meant a device which is attached to the casing or liner before the casing or liner is lowered into the bore hole, and which is operated to provide a passage (duct) between the interior of the casing or liner and the wall of the formation to be tapped for oil. Oil ows from the formation, through the passage, and into the casing or liner, to rise to the surface or to be pumped to the surface. The passage may be used to treat the oil bearing formation, as with, say, acids. Other stimulating agents may be used.

In practice, a number of devices are used, being so disposed along the length of the casing or liner as to be presented to the various superposed oil bearing strata to be tapped.

The object of the invention is to improve on some of my prior duct-forming devices, in that the device now disclosed is particularly adapted to be used where the oil bearing strata consist of running or unconsolidated sand, flour sand or silt. More particularly, the -device includes a lter.

In one form, the filter is used when the oil-bearing strata contain running or unconsolidated sand. In a modified form of the filter, it is used when the oil-bearing strata consist of flour sand.

In the drawings, wherein like numerals of reference indicate corresponding parts in the various figures,

FIGURE l is a more or less diagrammatic view showing a cemented hole with a casing having duct-forming devices;

FIGURE 2 is a partial horizontal section of the well hole, with one form of the device of the invention mounted on the casing and being in normal, non-extended (non-operational) position; and,

FIGURE 3 shows a modied form of the inner sleeve.

Referring to the drawing for the purpose of illustration, a bore hole is drilled in the earth 11 by any conventional drilling apparatus, A bore hole casing or liner 12 is positioned in the bore hole 10. An annular space is thus provided between the outer surface of the casing or liner 12 and the wall of the bore hole 10. The casing or liner 12 is sealed to or set in the formation 11 by means of cement 13. The cement 13 may be Portland cement or any other composition or settable material not adversely affected by oil, gas, or bore hole treating chemicals.

Oil and gas zones usually have a plurality of oil or gas producing bands or strata, indicated lby the numeral 14. Some of the strata 14 may be more porous than other adjacent strata. Where a bore hole traverses several strata of different permeabilities and the strata are to be stimulated, that is, treated by acids or other chemicals (or, as is practised in America, by Frac-ing), it is desirable that the cement seal 13 be maintained unbroken so that upon the application of treating materials or acids under pressure there will be no leakage outside of the casing 12 from one stratum 14 to another stratum 14 of greater permeability. In .actual practice, the strata 14 may be found to be of small thickness and possibly spaced only a few feet apart vertically.

The casing or liner 12 is provided, lbefore its introduction into the bore hole, with a plurality of duct-forming devices, made according to this invention, indicated by the numeral 15, disposed along the casing or liner 12 at 3,326,291 Patented June 20, 1967 lCC levels to correspond with the levels of the strata 14 to be treated and tapped; or, if preferred, the duct-forming devices may be arranged in a certain pattern, so that there may be so many devices per stratum according to its thickness.

The duct-forming device will be described first with reference to its original position, and in the form shown in FIGURE 2. It is preferable to mount the duct-forming device in a ring or guard G having a curved surface S welded to the outer surface of the casing or liner 12. The device includes a number of telescoping sleeves mounted in a bushing 16. The guard is formed with sloping sides F to facilitate the lowering of the casing or liner 12 into the bore hole. The guards serve to space the casing or liner 12 from the wall of the bore hole and tend to center it. The bore of the guard is centrally located with respect to the axis of an opening 40A in the casing or liner 12. I-t is provided with internal threads 17, and a shoulder 18 which is adapted to be engaged by the bushing 16 of the device when the bushing is threaded home into the bore of the guard.

A suitable O ring (a gasket) 56 housed in a groove formed in the bushing serves to provide a fluid-tight connection lbetween the bushing and the guard. The bushing 16 has recesses 22 for the application of a wrench to tighten the duct-forming device in the mounting guard G.

The surface of the bore of the bushing 16 is provided with a plurality of annular grooves 31, forming a serrated inner surface. The grooves present forward frustoconical surfaces T inclined downwardly toward the outer end of the device, and rearward surfaces P substantially perpendicular to the axis of the device.

A sleeve 21, formed with an enlarged rear portion 37 having an annular groove 39 in its outer surface near its inner end, is slidably mounted within the bushing 16. The groove 39 is in part dened by a surface X inclined to the vertical and directed upwardly toward the outer end of the device. A split spring ring 32 is carried in the groove 39 and, under tension, normally engages in one of the grooves 31 of the bushing 16, contracting and riding succesively over the inclined frusto-conical surfaces T of such grooves 31 as the sleeve 21 is moved outwardly in the bushing 16. On the other hand, if the sleeve tends to move inwardly in the bushing, the inclined cam surface X of the groove 39 exerts a force on the ring 32 upwardly and rearwardly, normal to the cam surface and the sleeve is thus prevented from moving inwardly in the bushing. The split ring 32 thus serves as a locking member preventing rearward (inward) movement of the sleeve in the bushing after the sleeve has moved outwardly in the bushing.

The outer sleeve 21 is formed with a rectangular groove 30 adjacent its inward (rear) end. In the groove is seated a split ring-like wire of square or rectangular cross section. In practice, the wire is made of magnesium. The wire bears against a shoulder formed into the bushing, so that the sleeve is prevented from moving outwardly in the bushing until the wire is sheared cfr. It has been found that a wire of square or rectangular cross section is much more satisfactory than a wire of circular cross section, in that its shearing strength for a given width (thickness) and given composition, does not vary in practice. A wire of circular cross section, on the other hand, since it will not always shear exactly along its exact longitudinal center, did vary considerably in its shearing strength. Also, by using such a shear device, that is, a length of wire formed into the shape of a split ring the required shearing strength can be easily computed since it is, for a given composition, and a selected thickness, a measure of the length of the wire. In practice the wires 100 will shea-r, t0 release the sleeves, when the fluid pressure within the casing 12 is between 1500 and 1800 pounds per square inch.

The outward movement of the sleeve 21 in the bushing 16 is determined (arrested) by the engagement of the enlarged portion or shoulder 37 with the inner end of the plain or unserrated front bore portion of the bushing 16.

The bushing 16 is provided with a groove containing an O-ring 34 engaging the outer surface of the sleeve 21 to form a pressure seal between the bushing and the sleeve.

The sleeve 21 has its inner bore provided with a plurality of annular grooves 36 similar to the grooves 31 of the bushing 16.

An inner sleeve 40 is slidably mounted within the sleeve 21. The sleeve 40 is provided wit-h a groove 39A similar to the groove 39 of the bushing 16, and a split spring ring 32A. This ring also serves as a locking member preventing inward movement of the sleeve 40 in the sleeve 21.

The sleeve 40 is also formed with a rectangular groove 30A adjacent its inward (rear) end in which is seated a length of wire 100A of square or rectangular cross section for the purpose served by the wire 100` and groove 30 aforesaid, that is, to free the sleeve 40 for outward movement relatively to the sleeve 21 as the Wire shears upon `application of a predetermined uid pressure within the casing.

The sleeve 21 is provided with a groove in which is an O-ring 37A to engage the outer surface of the sleeve 40 t-o provide a Huid-tight seal.

The outward movement of the sleeve 40 within the sleeve 21 is determined (arrested) by the engagement of the raised portion 37 of the sleeve 40 with the inner end of the plain or unserrated front bore of the outer sleeve 21.

'I'he outer sleeve 21 and the inner sleeve 40` are provided with channels 48.'Thus, communication passages are provided between the annular space between the bushing 16 and the outer sleeve 21, and the annular space between the two sleeves 21 and 40, and atmosphere, such passages forming exits for grease or other suitable compound packed in the annular spaces as the outer sleeve moves outwardly within the bushing and as the inner sleeve moves outwardly within the outer sleeve.

The compound is used to protect the acid-soluble parts of the device before it is used. It may comprise sweet glycerine and powdered limestone.

Applied to the inner (rear) end of the device, more particularly, to the bushing 16, is a thin metal cap 25, of magnesium. The cap may be one which is snapped on. In practice, the cap has a small orifice. The cap provides a closure for the inner end of the device.

The inner sleeve 40, in the form of a hollow cylinder, may be made of steel. The end (forward) wall is provided with a number of openings-I use four-which are closed by acid-soluble rivet-like plugs 50. In practice, the plug is formed with a head 51, presenting an outer coneshaped nose, and a shank 52 riveted against the inside face of the end wall. Thus, the wall of the formation is engaged by pointed plugs when the duct-forming device has been operated to its operative, formation-engaging position` The inner open end of the sleeve is closed by a plug or cap 53, which is dissolvable in the acid used to dissolve the pointed plugs 50. Once the plugs 50 and the cap or closure 53 have been dissolved, there is provided a duct or channel through the inner sleeve 40 through which acid may pass to be forced into the stratum (of the formation) to be treated, and oil may flow into the 'casing from the stratum.

After the plugs 50 have been dissolved away by acid to `clear or open the openings, the perforated wall operates as a -ilter or sieve, filtering such particles of sand or solid earth as are -too large to pass through the openings.

In t-he alternative form shown in FIGURE 3, the cap 53 is made of steel, as is the sleeve, but the cap is provided with a number of openings closed by rivets or plugs 50A of the same metal as that of the plugs 50. Thus,

when the plugs 50 and 50A have been dissolved away, oil may pass through the device (more particularly, through the inner sleeve 40) through the several openings through the front wall of the sleeve, and through the rear cap. The chamber so formed within the sleeve is filled with an acid-insoluble filter such as small glass beads B. These beads prevent fine material, such as silt, 4being entrained by the oil, from owing through the filter and into the casing or liner of the wall. Such filters may be periodically cleaned, one by one, by pumping oil (say, with surfactals, etc.) through each device.

Operation After the casing or liner 12 has been lowered to its chosen position in the bore hole, resting upon the bottom of the well hole, a volume of sealing cement (such as will be required to iill the annular space to the height necessary to surround or encase the sleeves of the devices when the sleeves have been moved outwardly against the wall of the bore hole) is pumped into the casing or liner 12. On top of the cement, and separated therefrom by a cementing plug, is pumped acetic acid of 10 to 12% concentration, in a volume such as to cover all of the duct-forming devices when the cement has been displaced into the annular space to surround the sleeve..On top of the acetic acid and separated preferably by another cementing plug, is pumped a displacement uid until the cement is displaced to casing bottom; continuing pumping forces the cement through the bottom of the casing and up into the annular space. At this time, that is, when all of the cement has been raised into the annular space, the acetic acid rises above all of the devices 15 and the first mentioned cementing plug is seated below all of the devices 15. Further continued pumping creates a pressure buildup above the seated first cement plug of about 1500 to 1800l pounds per square inch which is necessary to shear the wires 1GO-100A, causing the sleeves to move outwardly through the liquid cement, the plugs 50y coming into engagement with the wall of the bore hole, the acetic acid filling the annular space within the bushing and the outer sleeve 21 and coming into contact with the exposed rear end of the plug 53. The action of the locking rings 32 and 32A prevents any inward movement of the sleeves 21 and 40.

The plug 53 and the plugs 50 may be made of magnesium, which is dissolvable in acetic acid. The thickness of the plug 53 and the thickness -of the plugs 50 are so chosen as to require a selected length of time for their dissolution. For instance, it may be decided that the acid should not eat through the plugs, `to open a passage from the casing to the wall of a bore hole, before a selected period of time (to enable the cement to set). Once all the plugs have been dissolved, opening a passage as aforesaid, acid may be pumped through the (now open) sleeve 40 to the formation, to treat the formation. On the other hand, oil exuded or flowing through the formation will enter the casing through the passage.

The embodiments of the invention in which an exclusive property or privilege is claimed are dened as follows:

1. In apparatus for use in a bore hole traversing porous strata to be tapped; a duct-forming device adapted to be supported by a bore hole casing and comprising, a bushing mountable in the wall of the casing, passage-forming means movable `outwardly in said bushing including a hollow cylindrical body adapted to engage the wall of the bore hole, said hollow cylindrical body being in part defined by a rearward closure and a forward closure, means constraining said body to an outward movement, and means releasably locking said body against outward movement, said forward closure having apertures closed by plugs of a chosen material which is dissolvable in a chosen acid in Awhich said hollow cylindrical body is not dissolvable whereby said closure, when said plugs are removed, serves as a filter through which oil must flow before entering Vsaid yhollow cylindrical body.

2. Apparatus as in claim 1, wherein said rearward closure is dissolvable in the chosen acid.

3. Apparatus as in claim 1, wherein said plugs are formed with pointed extremities extending forwardly `of said forward closure.

4. Apparatus as in claim 1, wherein said rearward closure has apertures closed by plugs of said chosen material.

5. Apparatus as in claim 1, wherein the chamber defined within said body by said closures is lled with small bodies `to provide a filter.

6. Apparatus as in claim 5, wherein the small bodies consist of glass beads.

References Cited UNITED STATES PATENTS 2,944,791 7/1960 Le Bus 175-4 3,173,485 3/1965 Bretzke 166-100 3,245,472 4/ 1966 Zandmer 166-10() CHARLES E. OCONNELL, Primary Examiner.

10 N. C. BYERS, Assistant Examiner. 

1. IN APPARATUS FOR USE IN A BORE HOLE TRAVERSING POROUS STRATA TO BE TAPPED; A DUCT-FORMING DEVICE ADAPTED TO BE SUPPORTED BY A BORE HOLE CASING AND COMPRISING, A BUSHING MOUNTABLE IN THE WALL OF THE CASING, PASSAGE-FORMING MEANS MOVABLE OUTWARDLY IN SAID BUSHING INCLUDING A HOLLOW CYLINDRICAL BODY ADAPTED TO ENGAGE THE WALL OF THE BORE HOLE, SAID HOLLOW CYLINDRICAL BODY BEING IN PART DEFINED BY A REARWARD CLOSURE AND A FORWARD MOVEMENT, AND CONSTRAINING SAID BODY TO AN OUTWARD MOVEMENT, AND MEANS RELEASABLY LOCKING SAID BODY AGAINST OUTWARD MOVEMENT, SAID FORWARD CLOSURE HAVING APERTURES CLOSED BY PLUGS OF A CHOSEN MATERIAL WHICH IS DISSOLVABLE IN A CHOSEN ACID IN WHICH SAID HOLLOW CYLINDRICAL BODY IS NOT DISSOLVABLE WHEREBY SAID CLOSURE, WHEN SAID PLUGS ARE REMOVED, SERVES AS A FILTER THROUGH WHICH OIL MUST FLOW BEFORE ENTERING SAID HOLLOW CYLINDRICAL BODY. 